Chemoattractant cytokines or chemokines are small, secreted proteins that activate leukocytes. Aberrant chemokine responses contribute to inflammatory diseases such as asthma and atherosclerosis. A growing body of evidence implicates the PI3-kinase (PI3-K) pathway as a critical mediator of chemokine signaling in leukocytes. Our preliminary data suggest that both chemokines and PI3-kinase potently activate Integrin Linked Kinase (ILK) in leukocytes, and that this has important functional consequences. ILK is a 59 kDa serine/threonine kinase, that also interacts with both beta integrins and actin binding proteins. Based on in vitro studies utilizing gene transfer in human leukocyte cell lines, as well as genetically engineered ILK-deficient murine leukocytes, we hypothesize that ILK serves as a counter-regulatory, negative modulator of adhesion that facilitates subsequent transendothelial migration and chemotaxis. We further hypothesize that these functions are dependent on ILK kinase activity and will result in abnormalities of in vivo trafficking in inflammatory models. To test these hypotheses, we will utilize murine models of leukocyte-specific ILK deletion and gene transfer in combination with in vitro and in vivo models of leukocyte trafficking and inflammation. In Specific Aim 1, we will assess the functional effects of ILK deficiency on leukocyte recruitment in chemotaxis and adhesion assays in vitro. In Specific Aim 2, we will define the downstream mechanisms by which ILK modulates leukocyte chemotaxis and adhesion. In Specific Aim 3, we will test whether the in vitro functional effects observed in ILKdeficient leukocytes are recapitulated in inflammatory models in vivo. Understanding the role of specific signaling pathways in leukocyte recruitment may provide new targets for the management of many inflammatory disorders.